OpenEuphoria

RE: Uninitialized Variables

• Posted by Chris Bensler <bensler at mail.com> Mar 23, 2002
• 463 views

Derek Parnell wrote:
> ----- Original Message -----
> From: "Chris Bensler" <bensler at mail.com>
> To: "EUforum" <EUforum at topica.com>
> Sent: Sunday, March 24, 2002 10:58 AM
> Subject: RE: Uninitialized Variables
> 
> 
> > Derek Parnell wrote:
> > > ----- Original Message -----
> > > From: "Andy Serpa" <renegade at earthling.net>
> > > To: "EUforum" <EUforum at topica.com>
> > > Sent: Sunday, March 24, 2002 10:18 AM
> > > Subject: RE: Uninitialized Variables
> > >
> > >
> > > > > Apparently NAN is (silly me) Not A Number! :P
> > > > > using equal() compares NAN properly and consistently
> > > > >
> > > > > Here is my revised uninitialized values for variables:
> > > > >
> > > > >    integer  = -INF
> > > > >    atom     =  INF
> > > > >    sequence =  NAN
> > > > >    object   = -NAN
> > > > >
> > > >
> > > > So how do I test if something is a nan?  The "official" way is to use
> > > > x!=x, but that is usually optimized away by most compilers (&
> Euphoria,
> > > > apparently.)  Using something like if x=1 and x=2 will work in the
> > > > interpreter, but not translated to C, even with Watcom.  (In fact, it
> is
> > > >
> > > > different depending on the compiler).
> > > >
> > > > Am I stuck with "if x and compare(x/x,1)"?
> > > >
> > > > For my genetic programming system this is a very real problem, as it
> > > > comes up with random mathmatical expressions that sometimes are nan's.
> > > > If you then take a predicted value (which is a nan) as output for a
> > > > function that it has created and compare it with a target value, it
> will
> > > >
> > > > show as being equal (& therefore error = 0).  So functions with nan's
> as
> > > >
> > > > output get the highest fitness, which is a disaster...
> > > >
> > >
> > > This seems to work:
> > > --------------
> > > atom x,nan,inf
> > > inf = 1e300 * 1e300
> > > nan = inf / inf
> > >
> > > x = nan
> > >
> > > if x = nan then
> > >     puts(1, "x is not a number\n")
> > > end if
> > > ? x = nan
> > > ? x != nan
> > >
> > > ? nan
> > > ? inf
> > > ------------
> > >
> > >
> > Derek, try this.
> >
> > ? x=nan
> > ? x=inf
> > ? x=10
> >
> > btw:   nan = -(inf/inf)
> >
> >
> > Chris
> >
> >
> Okay, I did those changes and now I get this:
> 
> x is not a number
> y is a number
> 1
> 0
> 0
> 1
> 0
> 1
> 1
> 0
> 0
> nan
> inf
<snip>

it's not a CPU thing.

This works for me...

-------------------
atom x,y,nan,inf
inf = 1e300 * 1e300
nan = -(inf / inf) -- ( inf / inf = -nan )

? equal(10,nan)
? not equal(10,nan)
? equal(nan,nan)
-------------------

my results are:
0
1
1


Chris